The present invention concerns a coolable component of a gas turbine, which component has a hot gas flowing completely or partially around it during operation, which component is provided in its interior with at least one hollow space, through which hollow space a coolant flows during operation, which hollow space is connected to means for supplying the cooling medium and means for carrying away the cooling medium, which means form a flow path for the cooling medium. It also concerns a method of controlling the supply of cooling air, as well as a method of producing the component according to the invention.
The high efficiency and the power density of modern heat engines require high temperatures of the operating fluids, which in many cases exceed the permissible material temperature of materials which can be commercially used. This applies in particular in gas turbine technology.
The currently customary thermodynamic states of the hot gas in gas turbines require efficient cooling of the components in contact with the hot gas. The thermally highly loaded components are in this case cooled either purely convectively or by a combination of convection cooling and film cooling.
The already compressed air taken from the process for cooling is at least partially lost from the operating process, which has adverse effects in particular on efficiency. On the other hand, inadequate cooling reduces the service life of the component considerably. The cooling of the particularly stressed guide blades of the first turbine stage of a gas turbine is therefore designed for the hottest temperature to be expected of the oncoming hot gas flow. At the same time, a circumferentially very inhomogeneous temperature field must be expected right at the combustion chamber exit. To ensure adequate cooling of the blades subjected to the highest loading in each case, other blades are supplied with significantly more cooling air than is necessary.
Furthermore, the very different operating conditions must also be taken into account. Even when an engine is being operated in part-load mode with reduced hot gas temperatures, the cooling air fraction remains largely constant, in other words significantly more cooling air is used up than would be necessary for maintaining adequate cooling. Similarly, engines are cooled independently of the actual load cycles, in such a way that the highest possible component service life is achieved in a base-load/full-load machine even when the operator would accept a shorter service life of the component in the interests of higher efficiency and higher effective output.
To sum up, it remains to be stated that, according to the prior art, the cooling of the thermally highly loaded components of a gas turbine takes place in accordance with a rigid regime. In this regime, the amount of cooling air tends to be overdimensioned at the expense of the efficiency of energy conversion. On the other hand, it would be desirable to vary and control the amount of cooling air according to the actual circumstances and the operating conditions.
This is where the invention comes in. The aim of the present invention is thus to specify a coolable component of a gas turbine, which component has a hot gas flowing completely or partially around it during operation, which component is provided in its interior with at least one hollow space, through which hollow space a coolant flows during operation, which hollow space is connected to means for supplying the cooling medium and means for carrying away the cooling medium, which means form a flow path for the cooling medium, and in the case of which component the cooling air fraction is variable.
This is achieved according to the invention by there being in the flow path at least one restricting point for the cooling medium, which is adjustable during the operation of the gas turbine.
Furthermore, the invention includes a method of controlling the amount of cooling air, as well as a method of producing the component according to the invention.